In this thesis we explore precision in measurement of buffer overflow and loss probability. We see how buffer overflow probability compares with queuing delay measurements covered in the literature. More specifically, we measure the overflow probability of a packet buffer for various sampling rates to see the effect of sampling rate on the estimation. There are various reasons for measurement in networks; one key context assumed here is Measurement Based Admission Control. We conduct simulation experiments with analytically derived VoIP and bursty traffic parameters, in Matlab, while treating the buffer under consideration as a two-state Markov Chain. We note that estimation error decreases with increase in sampling gap (or in other words precision improves/variance decreases with decrease in sampling rate). We then perform experiments for VoIP and bursty data using NS-2 simulator and record the buffer states generated therein. We see a similar trend of increase in precision with increase in sampling gap. In our simulations, we have mainly considered static traffic passing through the buffer, and we use elastic traffic (TCP) for comparison. We see from our results that the sampling error becomes constant beyond certain asymptotic level. We thus look into asymptotic error in estimation,for the lowest sampling gap, to establish a lower bound on estimation error for buffer loss probability measurement. We use formulae given in recent literature for computing the experimental and theoretic asymptotic variance of the buffer state traces in our scenarios. We find that the theoretical and experimental asymptotic variance of overflow probability match when sampling a trace of buffer states modelled as a two-state Markov Chain in Matlab. We claim that this is a new approach to computing the lower bound on the measurement of buffer overflow probability, when the buffer states are modelled as a Markov process. Using Markov Chain modelling for buffer overflow we further explore the relationship between sampling rate and accuracy. We find that there is no relationship between sampling gap and bias of estimation. Crucially we go on to show that a more realistic simulation of a packet buffer reveals that the distribution of buffer overflow periods is not always such as to allow simple Markov modelling of the buffer states; while the sojourn periods are exponential for the smaller burst periods, the tail of the distribution does not fit to the same exponential fitting. While our work validates the use of a two-state Markov model for a useful approximation modelling the overflow of a buffer, we have established that earlier work which relies on simple Markovian assumptions will thereby underestimate the error in the measured overflow probabilities.

Este trabalho apresenta um método para prevenir as vulnerabilidades causadas por erros de programação insegura que, normalmente, é resultado da solução de um problema proposto ou do desenvolvimento de funcionalidade sem levar em consideração a segurança do sistema como um todo. Os erros de programação (no contexto da segurança de um sistema e não apenas da sua funcionalidade) são normalmente frutos da ignorância do programador sobre as vulnerabilidades apresentadas pelas suas ferramentas para construção de programas. O estado da arte é brevemente apresentado demonstrando as soluções atuais em termos de proteção contra ataques de buffer overflow baseado em pilha. Soluções em tempo de compilação e pós-compilação por parte do sistema operacional são as mais comuns. Neste escopo é demonstrada a solução proposta por um protótipo funcional que valida o modelo para uma série de aplicações em duas plataformas diferentes (Windows e Linux). A solução converge a instrumentação de aplicações com o uso de um repositório de endereços de retorno para prevenir o retorno de funções a endereços não legalmente especificados. Testes do protótipo foram realizados em ambas as plataformas e mostraram a eficácia do protótipo prevenindo falhas em casos reais de buffer overflow baseado em pilha. / This paper presents a method to prevent the vulnerabilities caused by insecure programming which, usually, is an outcome of taking into account only the solution of a proposed problem or the development of new functionalities disregarding security on development of the system as a whole. The programming mistakes (in the context of the system security despite the system's functionality) are usually a result of the unawareness of the programmed about the vulnerabilities contained on the tools they use to develop software. The state of the art is briefly presented showing the current solutions related to preventing buffer overflows based on stack. Both compile time and post-compilation solutions (usually as part of the operating system) are the most widely used. In this work the proposed solution is demonstrated by a functional prototype which validates the model for a set of applications in two different platforms (Windows and Linux). The solution converges process instrumentation with a return address repository to prevent a function from returning to an address not legally specified. Testes of the prototype were performed in both platforms previously mentioned and have proved the correctness of the prototype by actually preventing exploitation on real case scenarios of real world applications.

O Roteamento Global é responsável pelo planejamento da distribuição dos meios de interconexão dentro da área do circuito. Dentro da fase do projeto de circuitos conhecida como Síntese Física, essa fase situa-se após a etapa de posicionamento, que define uma posição exata para cada célula do circuito, e antes da etapa de roteamento detalhado que irá definir uma posição para cada meio de interconexão. Os roteadores globais utilizam uma versão abstrata e simplificada do circuito, que agrega uma região e toda a capacidade de fios que esta região comporta, trabalhando com o planejamento dessas capacidades em relação a demanda de interconexão entre as células do circuito. Este trabalho, apresenta um conjunto de técnicas para delimitação e tratamento de áreas que possuem alta demanda por meios de interconexão em circuitos VLSI. As técnicas são aplicadas em duas fases do fluxo de rotamento global: a primeira é executada na fase de pré-roteamento, onde são identificadas as regiões que possuem alta demanda por interconexão, isto é, são destino ou origem de um número elevado fios em relação a sua capacidade de alocar meios de interconexão; a segunda etapa ocorre dentro da fase de roteamento iterativo, identificando e protegendo aquelas que regiões que possuem os níveis mais elevados de congestionamento. Para avaliar os impactos da aplicação das técnicas propostas, foi feita a implementação em um fluxo de roteamento global existente. A avaliação foi partir da extração de quatro métricas de roteamento global comumente utilizadas na literatura de síntese física, para análise de roteamento global: comprimento dos fios, valor total de congestionamento, máximo congestionamento de aresta e tempo de execução. A partir da execução de experimentos utilizando as técnicas, foi possível verificar ganhos de até 11% em redução do congestionamento total no circuito, em benchmarks para os quais ainda não se tem soluções válidas na literatura. Os tempos de execução obtiveram um redução de até 35%, quando comparados com a implementação usada como referência para aplicação das técnicas, o roteador GR-WL. Um dos efeitos colaterais da aplicação de técnicas de calibração de custos é o aumento do comprimento médio dos fios. Os resultados dos experimentos mostram que as técnicas propostas conseguem reduzir este efeito colateral para, no máximo, 1.39% de acordo com os benchmarks executados. / Global routing phase is responsible for the interconnect planning and distribution across the circuit area. During the integrated circuit project flow, the global routing is contained in the Physical Synthesis, after the placement, that is when the position of all circuit cells are defined, and before the detailed routing, when the position of all interonnection wires is realized. A simplified and abstrate version of the circuit routing area is used by the global router, that will agregate in a single vertex, an specific region of the circuit, that represents a bunch of interconnection with their total capacity. This work presents a set of techniques to delimit and threat areas that have high interconnection demand in VLSI circuits. These techniques are applied in two steps of the global routing flow: the first is executed during the initial routing, where the high interconnection demanding regions are identified. the second step is executed during the iterative routing, where the top offender regions are identified and heva their costs pre-allocated. In order to evaluate the impact of the proposed techniques, they are implemented in an existing global routing flow, and four metrics are collected: total wirelenght, execution time, total overflow and maximum overflow. Tha last two metrics will be different from zero just for the circuits that not have a valid solution. After the execution of the experiments it was possible to verify a reduction up to 11% in wirelenght, in some benchmarks that the literature do no have a valid solution. Furthermore, it was possible to verify a reduction up to 35% in the execution time, when compared to the reference implementation. Once we are including constraints in form of cost pre-allocation, it is possible to verify an wirelength increase in some cases. In this work, it was possible to observe a small presence of these side-effects, up to 1.39%, according to the executed benchmarks.

Antibiotic resistance is a major threat to human health. Clinical situations are the main focus for antibiotic resistance research, but understanding the spread of resistance in the environment is also vital. A major contributor to this spread is wastewater from combined sewer overflow (CSO) events. The effect of CSO events on antibiotic resistance in the James River near Richmond, Virginia was studied using genomic and microbiological approaches. The abundance of genes associated with resistance to quinolones (qnrA) and tetracycline (tetW) was strongly correlated with the presence of fecal indicator bacteria (E. coli abundance) as well as total nitrogen and phosphorus loads, which suggests an anthropogenic source of these genes. Abundance of the blaTEM gene, which confers resistance to β-lactam antibiotics, was elevated during CSO events and increased with precipitation and river discharge. Bacteria isolated during a CSO event were resistant to more antibiotics and had higher multi-drug resistance when compared to isolates from a non-event. This study demonstrated that CSO events are contributing to the spread of antibiotic resistance.

Memory errors are a common cause of incorrect software execution and security vulnerabilities. We have developed two new techniques that help software continue to execute successfully through memory errors: failure-oblivious computing and boundless memory blocks. The foundation of both techniques is a compiler that generates code that checks accesses via pointers to detect out of bounds accesses. Instead of terminating or throwing an exception, the generated code takes another action that keeps the program executing without memory corruption. Failure-oblivious code simply discards invalid writes and manufactures values to return for invalid reads, enabling the program to continue its normal execution path. Code that implements boundless memory blocks stores invalid writes away in a hash table to return as the values for corresponding out of bounds reads. he net effect is to (conceptually) give each allocated memory block unbounded size and to eliminate out of bounds accesses as a programming error. We have implemented both techniques and acquired several widely used open source servers (Apache, Sendmail, Pine, Mutt, and Midnight Commander).With standard compilers, all of these servers are vulnerable to buffer overflow attacks as documented at security tracking web sites. Both failure-oblivious computing and boundless memory blocks eliminate these security vulnerabilities (as well as other memory errors). Our results show that our compiler enables the servers to execute successfully through buffer overflow attacks to continue to correctly service user requests without security vulnerabilities. / Singapore-MIT Alliance (SMA)

Sammanfattning -  ”Mind the Gap”- En studie om samarbetet mellan byrå och kund. Seminarium: 31 maj 2012 Institution: Mälardalens högskola, Akademin för hållbar samhälls-och teknikutveckling Kurs: Kandidatuppsats i företagsekonomi med inriktning mot marknadsföring, 15 ECTS Författare: Alexandra Bergkvist, Jenny Bernhardsson, My Lundberg 21 April 1988   11 December 1987   23 September 1988 Handledare: Dan Linder Examinator: Cecilia Lindh Nyckelord: Arbetsprocess, kundrelation, gapet, dödvikt, spill, reklambyrå Problem: Studien behandlar relationen mellan reklambyråer och deras kunder, vilka problem som kan uppstå i samarbetsprocessen samt hur det är möjligt att undvika problem och därigenom ge förslag på eventuella förändringar i samarbetet. Problemformuleringen bygger på att identifiera gapet i arbetsprocessen Syfte: Identifiera var gapet i arbetsprocessen mellan kunder och byråer består av. Frågeställning: Vad består gapet i arbetsprocessen mellan kunder och byråer av? När uppstår gap? På vilka sätt kan de berörda parterna minska gapet? Metod: I uppsatsen tillämpas en kvalitativ metod för att förstå vad gapet i arbetsprocessen består av. Studiens empiriska del utgörs av fyra personintervjuer, tre reklambyråer och en byråvalsrådgivare. Intervjufrågorna är av en halvstrukturerad intervjuform, vilket innebär att samma frågor, med frihet till följdfrågor kommer ställas. Slutsats: Bland de intervjuade byråerna och byråvalsrådgivaren rådde det en samstämmighet av vad gapet består av, med undantag av ett fåtal skilda meningar. Det framkom att gapet främst består av skild syn på förväntningarna i samarbetet. / Abstract - ”Mind the Gap”- A study on the cooperation between advertising agencies and their clients. Seminar date: May 31th 2012 Institution: University of Mälardalen, School of Sustainable Development of Society and Technology Course: Bachelor thesis in business administration focusing on marketing, 15 ECTS Authors: Alexandra Bergkvist, Jenny Bernhardsson, My Lundberg 21 th April 1988   11th December 1987   23rd September 1988 Tutor:  Dan Linder Examinator: Cecilia Lindh Keywords: Work process, Customer Relations, Gap, Deadweight, Overflow, Advertising agency Problem: The problem formulation is based on identifying the gap in the work process between advertising agencies and their clients. Purpose: The purpose of this study is to identify what the gap in the work process between clients and advertising agencies consists of. Research question: What does the gap in the work process between clients and advertising agencies consists of? When does gaps occur? In what way can the two parts bridge the gap? Method: The paper applies a qualitative method for understanding what the gap in the work process consists of. The empirical part of the study consists of four personal interviews, with three advertising agencies and one agency-choice counsellor. The interview questions are of a semi-structured interview form, which means that the same questions will be asked but with freedom to ask follow-up questions. Conclusion: Among the interviewed agencies and the agency-choice counsellor, there was a consensus of what the gap consists of, with the exception of a few different opinions. The appearance showed that the gap mainly consisted of different expectations and visions.

Cold laps are defined as micro-lack of fusion defects at the weld toe more or less parallel to the surface of the parent plate. These defects are known to negatively influence the fatigue properties of weldments. Previous studies suggest that cold lap formation can not be avoided completely in Gas Metal Arc Welding (GMAW). Therefore, a better understanding of formation mechanisms is imperative to be able to minimize the number and size of these defects. The main objective of this work has been to provide a more comprehensive understanding of cold laps, including categorising, characterisation and defining the most significant factors for formation. GMAW was used to produce welds that were investigated by metallographic methods using light optical microscopy, scanning electron microscopy and energy dispersive spectrometry. A novel classification of cold laps was introduced and three types of cold laps were identified: spatter cold laps, overlap cold laps and spatter-overlap cold laps. It was shown that cold laps are partially or fully filled by oxides. The most common oxides are manganese silicon oxides which were concluded to be formed primarily by oxidation of droplets. The presence of oxides was found to significantly increase the tendency to form spatter cold laps as well as overlap cold laps. Particularly for overlap cold laps, it was found that the depth (in transverse direction of weld) is reduced when welding in a non-oxidising environment. Welding on blasted surfaces increased the cold lap formation by entrapment of gas. The droplet and base metal temperatures were also found to be significant factors in cold lap formation. For overlap cold laps the occurrence frequency decreased with increased preheating temperature of the base metal. Mechanisms of overflowing resulting in overlap cold laps were discussed based on an extensive literature review. Several phenomena are believed to contribute to overflow including Rayleigh instability, the balance of forces, transfer of lateral momentum by droplets and an outward Marangoni fluid flow of the weld pool. The present studies suggest that cold lap formation can be suppressed by ensuring that the welding process (arc) is as stable as possible and by welding on a preheated work piece in a non-oxidising environment.

No description available.

This study showed that hydrodynamic particle breakage had potential as a method to help improve the disinfection of wastewater effluents. The physicochemical properties of flocs from four distinct effluents sources (combined sewer overflow, settled combined sewer overflow, primary effluent, and final effluent) were compared before and after hydrodynamic treatment. The use of hydrodynamic force to cause floc breakage was shown to be effective, though variable, across all source types. This variation in floc breakage did not have a significant impact on the UV disinfection achieved, as the UV dose kinetics were similar across samples from the same source type. The results of this study demonstrate how the physicochemical properties of floc are affected when exposed to shear force. These observations further the understanding of floc composition and behaviour when shear forces are applied while also providing evidence to indicate this process improves the performance of UV disinfection technology.

Dauguma hidrotechnikos statinių naudojami daugiau negu 30 metų. Praktiškai kiekviename statinyje yra gelžbetoninių konstrukcijų. Gelžbetonis yra patvari medžiaga, tačiau ilgainiui dėl įvairių priežasčių (natūralus medžiagų senėjimas, įvairios apkrovos ir veiksniai: mechaniniai, fiziniai, cheminiai, specifiniai), konstrukcijose, pagamintose iš šios medžiagos, atsiranda pokyčių bloginančių statinio naudojimo savybes, trumpinančių gyvavimo trukmę. Betono ir gelžbetonio irimo procesai labai sudėtingi, nes kartu veikia daug įvairių veiksnių, keičiančių fizines ir mechanines savybes. Todėl konstrukcijų patvarumas priklauso nuo šių irimo procesų intensyvumo. Konstrukcijų patvarumo esminiai reikalavimai pateikiami statybos reglamente STR 1.12.05:2010. Tyrimo tikslas – ištirti, įvertinti ir palyginti Marijampolės, Šakių, Vilkaviškio, Kėdainių rajonų slenkstinių pralaidų būklę su ankstesnių tyrimų rezultatais. Mokslinių ekspedicijų metu 2011 – 2012 m. vizualiai buvo ištirtos dešimties slenkstinių pralaidų būklė, jų amžius yra 50 – 60 metų, seniausia 76 metai. Tiriant slenkstinių pralaidų pažaidų būklės kitimą buvo naudoti šie konstrukcijų diagnostikos metodai: kameraliniai darbai; vizualinis metodas; neardantis metodas betono stipriui nustatyti (instrumentinis); slenkstinių pralaidų techninė būklė įvertinta balais pagal STR.1.12.03:2006 pateiktą metodiką; statistiškai apdoroti duomenys „MS EXCEL“ kompiuterine programa. Palyginus 2011 – 2012 m. tyrimų su ankstesnių (1999 – 2009 m... [toliau žr. visą tekstą] / Most hydraulic structures are used by more than 30 years. Practically every building is of reinforced concrete structures. Reinforced concrete is a durable material, but eventually for various reasons (natural aging of materials, loading and various factors: the mechanical, physical, chemical, specific) changes occur in the structures made of these materials worsening usage properties of the structure, shortening the life span. Concrete and reinforced concrete degradation processes are very complicated because a variety of factors that change the physical and mechanical properties operate at the same time. Therefore, the durability of structures depends on the intensity of decomposition processes. Essential requirements of structural stability are presented in the construction regulation STR 1.12.05:2010. The aim of the research was to investigate, evaluate and compare condition of overflow spillways situated in Marijampolė, Šakiai, Vilkaviškis and Kėdainiai districts with previous results. During scientific expeditions in 2011 – 2012 the condition of ten overflow spillways were examined visually, their age is 50 – 60 years old, the oldest is 76 years old. Studying condition changes of the damages in overflow spillways the following structure diagnostic methods were used: Indoor works; Visual method; Non-destructive method for the determination of the strength of concrete (instrumental); The technical condition of overflow spillways was evaluated by scoring... [to full text]